The invention is generally directed to toner and developer compositions, and more specifically, the present invention is directed to developer and toner compositions containing charge enhancing additives, which impart or assist in imparting a positive charge or a negative charge to the toner resin particles and enable toners with rapid admix characteristics. In one embodiment, there are provided in accordance with the present invention toner compositions comprised of resin particles, pigment particles, and dendrimers as illustrated, for example, in U.S. Pat. No. 5,098,475 and U.S. Pat. No. 5,120,361, the disclosures of which are totally incorporated herein by reference. In these patents, there are illustrated inks with dendrimers, and more specifically, in U.S. Pat. No. 5,098,475, the disclosure of which is totally incorporated herein by reference, there is disclosed an ink composition which comprises an aqueous liquid vehicle and a colored dendrimer, or dendricolorant obtained by attaching a reactive dye or dyes to commercially available amino terminated dendrimers, that is for example a dendrimer having an amine group like NH.sub.2 attached to the end of the arm farthest removed in distance from the core, which dendrimers can be of the first, second, third, or n-th generation, wherein n is a number of preferably less than 9, and more specifically is a number of from about 1 to about 8, and wherein the attachment reaction can be accomplished at room temperature in water. The resulting dispersion of colored dendrimers can be formulated into an ink by the addition, for example, of a cosolvent comprised of water and a glycol, like diethylene glycol, thereby improving latency, which is the maximum time period, for example less than one hour, and from about 1 to about 10 minutes, over which an uncapped ink jet printhead can remain idle before noticeable deterioration of its jetting performances, and this addition can improve ink drying time, that is the time needed for an ink jet print to dry to an extent such that it will not smear or offset upon handling or when placed in contact with another sheet of paper, which drying time can, for example, be less than one minute, or more specifically from about 10 to about 30 seconds.
The aforementioned additives in embodiments of the present invention enable, for example, toners with rapid admix of less than about 60 seconds, extended developer life, stable electrical properties, excellent flow characteristics, and high image print quality with substantially no background deposits. Also, the dendrimers can be incorporated into the toner in small effective amounts, such as 0.01 weight percent of the toner, and the dendrimers are nontoxic and environmentally safe as compared to, for example, charge additives of metal complexes like chromium salicylates which are considered unsafe environmentally. The aforementioned toner compositions usually contain pigment particles comprised of, for example, carbon black, magnetites, or mixtures thereof, cyan, magenta, yellow, blue, green, red or brown components, or mixtures thereof providing for the development and generation of black and/or colored images. The toner compositions of the present invention in embodiments thereof possess excellent admix characteristics as indicated herein, and maintain their triboelectric charging characteristics for an extended number of imaging cycles. The toner and developer compositions of the present invention can be selected for electrophotographic, especially xerographic imaging and printing processes, including color processes.
Developer compositions with charge enhancing additives, which impart a positive charge to the toner resin, are known. Thus, for example, there is described in U.S. Pat. No. 3,893,935 the use of quaternary ammonium salts as charge control agents for electrostatic toner compositions. In this patent, there are disclosed quaternary ammonium compounds NR.sub.4 X with four R substituents on the nitrogen atom, which substituents represent an aliphatic hydrocarbon group having 7 or less, and preferably about 3 to about 7 carbon atoms, including straight and branch chain aliphatic hydrocarbon atoms, and wherein X represents an anionic function including, according to this patent, a variety of conventional anionic moieties such as halides, phosphates, acetates, nitrates, benzoates, methylsulfates, perchloride, tetrafluoroborate, benzene sulfonate, and the like; and U.S. Pat. No. 4,221,856 which discloses electrophotographic toners containing resin compatible quaternary ammonium compounds in which at least two R substituents are hydrocarbons having from 8 to about 22 carbon atoms, and each other R is a hydrogen or hydrocarbon radical with from 1 to about 8 carbon atoms, and A is an anion. There are also described in U.S. Pat. No. 2,986,521 reversal developer compositions comprised of toner resin particles coated with finely divided colloidal silica. Also, there is illustrated in U.S. Pat. No. 4,338,390, the disclosure of which is totally incorporated herein by reference, developer compositions containing as charge enhancing additives organic sulfate and sulfonates, which additives can impart a positive charge to the toner composition. Further, there is disclosed in U.S. Pat. No. 4,298,672, the disclosure of which is totally incorporated herein by reference, positively charged toner compositions with resin particles and pigment particles, and as charge enhancing additives alkyl pyridinium compounds. Additionally, other documents disclosing positively charged toner compositions with charge control additives include U.S. Pat. Nos. 3,944,493; 4,007,293; 4,079,014; 4,394,430; 4,560,635 which illustrates a toner with a distearyl dimethyl ammonium methyl sulfate charge additive; and U.S. Pat. No. 4,490,455 which discloses toners with, for example, amine salt charge enhancing additives, reference the Abstract of the Disclosure for example, and wherein the charge additive includes those derived from aromatic substituted sulfonic acids, such as benzene sulfonic acid, and the like, see column 3, beginning at line 33; and also known are bisulfate charge additives. Also, toners with dendrimers are particularly advantageous in that the toners can be prepared by in situ methods since, for example, the dendrimer can be applied as aqueous solutions to the toner suspension in water prior to toner drying. Many of the known charge additives are not as soluble in water as the dendrimers and/or they do not exhibit the same affinity for the toner surface in an aqueous environment, thus leading to nonuniform surface coverage and image resolution problems.
Moreover, toner compositions with negative charge enhancing additives are known, reference for example U.S. Pat. Nos. 4,411,974 and 4,206,064, the disclosures of which are totally incorporated herein by reference. The '974 patent discloses negatively charged toner compositions comprised of resin particles, pigment particles, and as a charge enhancing additive ortho-halo phenyl carboxylic acids. Similarly, there are disclosed in the '064 patent toner compositions with chromium, cobalt, and nickel complexes of salicylic acid as negative charge enhancing additives.
There is illustrated in U.S. Pat. No. 4,404,271 complex system for developing electrostatic images with a toner which contains a metal complex represented by the formula in column 2, for example, and wherein ME, the metal, can be chromium, cobalt or iron. Additionally, other patents disclosing various metal containing azo dyestuff structures wherein the metal is chromium or cobalt include U.S. Pat. Nos. 2,891,939; 2,871,233; 2,891,938; 2,933,489; 4,053,462 and 4,314,937. Also, in U.S. Pat. No. 4,433,040, the disclosure of which is totally incorporated herein by reference, there are illustrated toner compositions with chromium and cobalt complexes of azo dyes as negative charge enhancing additives.
Illustrated in U.S. Pat. No. 4,937,157, the disclosure of which is totally incorporated herein by reference, are toner compositions comprised of resin, pigment, or dye, and tetraalkyl sulfates, wherein alkyl, for example, contains from 1 to about 30 carbon atoms, ammonium bisulfate charge enhancing additives such as distearyl dimethyl ammonium bisulfate, tetramethyl ammonium bisulfate, tetraethyl ammonium bisulfate, tetrabutyl ammonium bisulfate, and preferably dimethyl dialkyl ammonium bisulfate compounds where the dialkyl substituents contain from about 10 to about 30 carbon atoms, and more preferably dialkyl radicals with from about 14 to about 22 carbon atoms, and the like. The aforementioned charge additives can be incorporated into the toner or may be present on the toner surface.
Although many charge enhancing additives are known, there continues to be a need for toners with additives, which toners possess many of the advantages illustrated herein. Additionally, there is a need for positive or negative charge enhancing additives which are useful for incorporation into black, and/or colored toner compositions. Moreover, there is a need for colored toner compositions containing nontoxic dendrimer charge enhancing additives therein, or on the toner surface. There is also a need for toner compositions which toners in embodiments thereof possess acceptable substantially stable triboelectric charging characteristics, and excellent admixing properties. Moreover, there continues to be a need for positively or negatively charged toner and developer compositions. Further, there is a need for toners with nontoxic legally disposable charge enhancing additives which can be easily and permanently dispersed into toner resin particles. There also is a need for positively charged black and colored toner compositions that are useful for incorporation into various imaging processes, inclusive of color xerography, as illustrated in U.S. Pat. No. 4,078,929, the disclosure of which is totally incorporated herein by reference; laser printers; and additionally a need for toner compositions useful in imaging apparatuses having incorporated therein layered photoresponsive imaging members, such as the members illustrated in U.S. Pat. No. 4,265,990, the disclosure of which is totally incorporated herein by reference. Also, there is a need for toner compositions which have the desired triboelectric charge level, for example, from about 10 to about 40 microcoulombs per gram, and preferably from about 5 to about 25 microcoulombs per gram, and admix charging rates of from about 5 to about 60 seconds, and preferably from about 15 to about 30 seconds as determined by the charge spectrograph, preferably for example at low concentrations, that is for example less than 1 percent, and preferably less than about 0.1 percent of the charge enhancing additive of the present invention.